As part of its British heritage, the federal government and all states except Louisiana enjoy a legal tradition of common law. Under American common law, judicial decisions have the force of law within their respective jurisdictions. Therefore, reference to case law is a necessary part of American jurisprudence. The force of law derives from precedent and the doctrine of stare decisis (“stand on what has been decided”). These principles require that lower courts follow the decisions of higher courts and that the court follow its own past decisions in the absence of an irrefutable argument against it. In the states, the common law tradition also gives judges considerable discretion to make laws in important areas, such as trademarks and contracts.
All law in the United States is subject to the federal Constitution. When a conflict arises, applicable federal law overrides state law. However, only Supreme Court decisions are binding on the states. Decisions of federal intermediate appellate courts are binding only on federal district courts within the relevant region, but are not binding on state courts. Although the formulation of laws is clearly divided between the federal government and the states, adjudication is not. State courts are competent to hear suits brought under federal law, and federal courts are competent to hear suits brought under state law under certain general conditions, such as cases where the litigants come from different states.
Thus, the U.S. Constitution defines the hierarchy of federal law:
The U.S. Constitution is the fundamental law of the United States. Laws that conflict with the Constitution may be declared invalid by a court. There have been only 27 amendments since the Constitution was ratified, 10 of which were finalized at the same time, shortly after the Constitution was ratified.
Legislative acts are the general basis for federal legislation. Proposed legislation must go through Congress and be signed by the president. On the other hand, if the president rejects a piece of legislation that has passed through Congress, it can still become law if 2/3 of each house of Congress votes to invalidate such a veto. Legislative acts are published in the Code of Laws and codified in the United States Code (U.S.C.).
International treaties ratified by the Senate are treated as the hierarchical equivalent of legislative acts. Courts in the United States, based on the common law role of judges, will make every effort to interpret domestic law in a manner consistent with international obligations. However, when a treaty provision irreconcilably conflicts with a piece of legislation, what is later enacted is the law applied by the United States courts.
Regulations passed by federal agencies under the Administrative Procedure Act are enforceable, but they must be consistent with both the Constitution and statutory law. However, under the “Chevron doctrine” (Chevron), the judiciary reckons with a government agency’s reasonable interpretation of some statute under its jurisdiction. Statutory acts are published in the Federal Register and codified in the Code of Federal Regulations (C.F.R.).
Case law has legal force, which varies depending on the court issuing the decision. Case law is published in national, regional, or state “dockets,” and the dockets themselves are bound volumes of published court decisions. With respect to lower courts, not all decisions are published, and only those that are published have precedential value.
An independent evaluation of the laws of most states has revealed great discrepancies between the laws of the various states. Organizations such as the American Law Institute (ALI) and the Uniform Law Commission (ULC) have tried to create more uniform state laws through model laws and carefully reasoned summaries. ALI publishes the texts of the Body of Law, which summarizes the current state of a topic of American law according to the consensus of the U.S. legal community, and the Principles of Law, which frame the law as it should be framed, on topics that now need legal guidance.